Chapter 2: Chemicals of Life

A. Bonding

• 1. Covalent Bonds– 2 or more atoms share

electrons to form a molecule

– No net charge due to equal number of + and –

– Ex. water

Properties of Water

Covalent bonding vs. Hydrogen bonding

Covalent Bond

Hydrogen Bond

A. Bonding

• 2. Hydrogen Bonds• Weak bond between

polar molecules

A. Bonding

• 3. Ionic Bonds– Gained or lost one or

more electrons– Charged due to unequal

number of electrons or protons

– Ex. NaCl

B. Properties of Water

a. Water heats slow b. Retains heat longerc. Helps maintain

homeostasis

1. High Heat Capacity

B. Properties of Water

Water is the solvent of Life!

Solute – substance dissolved in a solvent to form a solution

Solvent – fluid that dissolves solutes

Example: Ice Tea – water is the solvent and tea and sugar the solutes

2. Universal Solvent

B. Properties of Water

a. cohesion = water attracted to other water molecules because of polar properties

ex. Forms drops or film•surface tension = water is pulled together creating the smallest surface area possible

b. adhesion = water attracted to other materialsex. Getting wet, capillary action

3. Cohesion, Adhesion and Surface Tension

B. Properties of Water

4. Capillary Action = Water molecules move due to adhesive and cohesive properties as a result of the original adhesion. Ex: Think water in a straw Ex: Water moves through trees this way

B. Properties of Water

• 5. Water is a polar molecule. – Many substances will

dissolve– Non-polar molecules will

not dissolve

C. Classes of Organic Molecules:

• What are the four classes of organic molecules?

• Carbohydrates• Lipids• Proteins• Nucleic Acids

1. Carbohydrates• Sugars• Carbo = carbon, hydrate = water; Oxygen• Functions:• Store energy in chemical bonds• Glucose is the most common

monosaccharide– Monosaccharides– Disaccharides– Polyshaccharides

1. Carbohydrates

• Benedicts Test

1. Carbohydrates

• Iodine – Starch test

2. Lipids• Structure: Greasy or oily nonpolar

compounds• Functions:• Energy storage • membrane structure• Protecting against drying out. • Insulating against cold.• Absorbing shocks.

2. LipidsSaturated and Unsaturated Fats

• Unsaturated fats :– liquid at room temp– one or more double bonds between carbons in the fatty acids allows for “kinks” in the tails– most plant fats

• Saturated fats:– have only single C-C bonds in fatty acid tails– solid at room temp– most animal fats

2. Lipids. • Phospholipids• Structure: Glycerol + 2 fatty acids + phosphate group.• Function: Main structural component of membranes, where they arrange in

bilayers.

3. Proteins

• Structure:• Polypeptide chains• Consist of peptide bonds between 20 possible

amino acids• Have a 3 dimensional globular shape

3. Functions of Proteins

• Enzymes speed up a chemical reaction• Structural materials– keratin (the protein found in hair and nails)– collagen (the protein found in connective tissue)

• Specific carriers –– Carry materials across cell membrane, carry

oxygen in blood

3. Proteins:• Structure of Amino Acid – Hydrogen – Amino group– Carboxyl (acid) group– Variable R group specific to each amino acid

4. Nucleic Acids• Two kinds:– DNA:

double strandedcan self replicatemakes up genes which code for proteinsis passed from one generation to another

– RNA:single stranded functions in actual synthesis of proteins coded for by DNAis made from the DNA template molecule